The present invention relates to a liquid ejecting apparatus comprising a liquid ejector for ejecting liquid from a head face of a liquid ejecting head onto a target medium, while reciprocating the liquid ejecting head in a primary scanning direction; a conveyance guide member for supporting in a slide contact manner the target medium from a backside of a target surface such that spacing between the head face of the liquid ejecting head and the target surface of the target medium should have a predetermined spacing; and a medium conveyer for conveying the target medium in a secondary scanning direction at a predetermined conveyance rate, while pressing the target medium against a slide contact face of the conveyance guide member.
In liquid ejecting apparatuses represented by ink jet recording apparatuses for performing recording by ejecting ink from a recording head onto a recording surface of a target medium such as recording paper, a problem arises in association with a phenomenon of so-called cockling which is caused when ink ejected onto the target surface is absorbed into the target medium. The cockling indicates the phenomenon that a portion of the target medium that has absorbed the ink expands and thereby causes corrugating deformation in the target medium. The target medium that suffers corrugating deformation is lifted from the slide contact face of the conveyance guide member, and thereby causes concern for so-called head rubbing that a part of the target surface of the target medium comes in contact with the recording head.
For example, Japanese Patent Publication No. 2003-326743A discloses an ink jet recording apparatus capable of performing so-called marginless recording in which recording is performed while discarding ink to the outside of the target medium so that recording is achieved without a blank space in the four side areas of the target medium. In the case of such marginless recording, the ink is ejected without a blank space over the entire surface of the target medium. This causes more easily the corrugating deformation by cockling.
In order to reduce such concern for head rubbing caused by cockling, Japanese Patent Publication No. 2002-52771A discloses a recording apparatus in which a plurality of ribs are arrayed at equal intervals in the primary scanning direction in accordance with the cockling of corrugating deformation generated at an approximately fixed pitch, while the ribs are arranged at a fixed pitch with a certain regularity in the positional relationship with a conveyance follower roller. A pressing force on a target medium exerted by a medium feeding roller and the ribs for supporting, from the backside of the target medium in a state that the pressing force is exerted, allow the cockling pitch in the target medium to agree approximately with the pitch of the ribs. This stabilizes the cockling pitch, and hence reduces concern that the target medium may swell to the recording head face side owing to the cockling and thereby cause head rubbing.
Nevertheless, in the corrugating deformation in the target medium caused by cockling, the shape of corrugating deformation does not become stable immediately at the moment that the liquid is ejected onto the target medium. The corrugating deformation in the target medium caused by cockling gradually changes starting at a time point that the liquid ejection begins. In a portion where the liquid ejection has completed, the deformation reaches a saturated state after a certain time period has elapsed from the time point of completion of liquid ejection. At that time, the corrugating deformation shape reaches a stable state. The time necessary for the corrugating deformation by cockling to reach the stable state varies depending on the quality of the target medium, the characteristics of the liquid, and the like.
Thus, in the configuration disclosed in Japanese Patent Publication No. 2002-52771A, in some cases depending on the type of the target medium, the characteristics of the liquid, and the like, the target medium is conveyed to a conveyance position where the pressing force on the target medium exerted by the medium feeding roller becomes weak, before the corrugating deformation by cockling becomes saturated so that the corrugating deformation shape becomes stable. This causes instability in the pitch of formed cockling so that the corrugating deformation does not agree with the ribs. Accordingly, concern arises that the target medium may be lifted and thereby cause head rubbing.